The effects of experimentally induced graded monocular and binocular astigmatism on near stereoacuity

PURPOSE: To determine the effects of experimentally induced graded monocular and binocular astigmatism on near Stereoacuity in healthy adults. METHOD: This prospective cross-sectional study was performed on 60 healthy adults ranging between 19 and 33 years of age recruited from College of Applied Medical Sciences. All subjects were emmetropic with normal binocular single vision, and stereoacuity of 40 sec of arc. Enrolled subjects were divided into four groups, each with 15 participants. Myopic astigmatism was induced in two groups, either monocularly or binocularly using +1.00 DC and +2.00 DC at different axes 45, 90 and 180. The remaining two groups were subjected to induced hypermetropic astigmatism using −1.00 DC and −2.00 DC at different axes 45, 90 and 180. The Titmus Fly Stereo Test was used to measure near stereoacuity both before and after induction of astigmatism. RESULTS: There was a reduction in stereoacuity with an increase in dioptric power of astigmatism (p < 0.05). In all groups, oblique astigmatism had the most significant effect followed by against the rule astigmatism and then with the rule astigmatism. Binocular induced hypermetropic astigmatism caused more reduction in stereoacuity than binocular induced myopic astigmatism, but statistically not significant. A similar impact was noted between monocular myopic astigmatism and monocular hyperopic astigmatism (p = 0.037), (p = 0.049) and (p = 0.044) with 2.00 D cylinder at 180, 90 and 45 axes, respectively. CONCLUSION: The results indicate that the small amount of monocular or binocular astigmatism will affect on Stereoacuity, and the amount of reduction varies according to the axis of orientation.